Spin-valve transistor

ABSTRACT

A spin-valve transistor has an emitter, a base including a spin-valve film in which two magnetic layers are stacked with interposing a nonmagnetic layer between the two magnetic layers, and a collector, the spin-valve film having a stacked structure of M/A/M′ or M/B/M′ and the spin-valve film being (100)-oriented, where each of M and M′ includes at least one element selected from the group consisting of Fe, Co, Ni and an alloy including Fe, Co, Ni, A includes at least one element selected from the group consisting of Au, Ag, Pt, Cu and Al, and B includes at least one element selected from the group consisting of Cr and Mn.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2000-200133, filed Jun.30, 2000, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a spin-valve transistor, whichcan be suitably employed, for example, in a magnetic head for readinghigh-density magnetic recording and in a high-density memory device suchas a magnetic RAM (MRAM) and a magnetic ROM (MROM).

[0004] 2. Description of the Related Art

[0005] Highly increased density and velocity of magnetic recording inrecent years can be mainly attributed to progress in magnetic recordingapparatuses, in particular, to progress in magnetic heads used forwriting and reading of magnetic recording as well as to improvement inmagnetic recording media. As the magnetic recording medium isincreasingly reduced in size and improved in capacity, a relativevelocity between the magnetic recording medium and the magnetic readinghead is decreased correspondingly. In order to provide a high outputeven under such a situation, a giant magnetoresistive head (GMR head)comprising a spin-valve film has been developed as a new-type readoutmagnetic head. The GMR head has excellent characteristics in that itprovides a high magnetoresistance ratio (MR ratio) compared with aconventional MR head. Recently, a GMR head of a tunnel junction typethat is expected to exhibit even better characteristics is attracting alot of attention.

[0006] Conventional magnetic recording media such as a magnetic disc isdesigned to function as a file memory, in which information storedtherein is once read into a semiconductor memory (DRAM or SRAM) of acomputer before the information is utilized. Certainly, thesemiconductor memory has various excellent characteristics, but isaccompanied with a defect in that it consumes high electric power formemory holding. In recent years, a flash memory and an FRAM, whichrequire no electric power for memory holding, have been developed, butthey have a drawback in that the number of rewrite operations is ratherlimited. On the other hand, endeavor to develop a magnetic memory(MRAM), which permits substantially infinite rewrite operations, hasbeen started. In order to realize the MRAM, however, development of amaterial or a device capable of exhibiting a high MR ratio is desired.

[0007] Under the circumstances, a magnetic tunnel junction element isnow attracting a lot of attention as an element exhibits a higher MRratio than the conventional spin-valve film. The magnetic tunneljunction element or a combination of the magnetic tunnel junctionelement and a MOS transistor has been used in attempts to fabricate amagnetic head or a magnetic memory. Further, development of a spin-valvetransistor capable of exhibiting a higher MR ratio than the magnetictunnel junction element has also been started.

[0008]FIGS. 1A and 1B show examples of band diagrams of conventionalspin-valve transistors.

[0009] The spin-valve transistor shown in FIG. 1A is of a type in whichelectrons are injected from an emitter via a tunnel junction into abase. This spin-valve transistor has a stacked structure of an Alemitter 11, a tunnel insulator 12, a base 13 comprising an Fe/Au/Fespin-valve film, and an n-Si collector 14.

[0010] On the other hand, the spin-valve transistor shown in FIG. 1B isof a type in which electrons are injected from an emitter via a Schottkyjunction into a base. This spin-valve transistor has a stacked structureof an n-Si collector 21, a base 22 comprising a Co/cu/Co spin-valvefilm, and an n-Si collector 23.

[0011] These spin-valve transistors are known to exhibit an extremelyhigh MR ratio of several hundreds percent. However, these conventionalspin-valve transistors have a defect in that a collector current (Ic) isextremely low, for example, in the level of about 10⁻⁴ of an emittercurrent (Ie). This low ratio of collector current/emitter current(Ic/Ie) is undesirable in view of power consumption, operating speed,noise, and so on.

[0012] The reason why the collector current is extremely low in theconventional spin-valve transistors can be explained as follows. Forexample, in the case of the spin-valve transistor shown in FIG. 1A inwhich electrons are injected from the emitter via the tunnel junctioninto the base, angle dependency of the tunnel current can be representedby the following equation:

J _(θ)∝exp[−β²sin² _(θ)]  (1)

[0013] where β⁴=2 ms²E_(F) ²/h²(E_(v)−E); θ is an angle formed betweenthe normal line to the junction surface and a wavenumber vector ofelectrons; J_(θ) is a current density in the direction of θ; m is themass of electron; s is a width of the tunnel barrier; E_(F) is Fermienergy; h is the Planck constant; E_(v) is a height of the tunnelbarrier; and E is energy of tunnel electrons.

[0014] It will be seen from this equation that, when the direction oftravel of electrons passing through the tunnel insulator is almostperpendicular to the junction surface, the tunnel current can beincreased. Even in the case of the spin-valve transistor shown in FIG.1B in which electrons are injected from the emitter via the Schottkyjunction into the base, the current can be increased when the directionof travel of electrons is almost perpendicular to the junction surface.

[0015] The spin-valve transistor is designed to operate based onspin-dependent scattering of electrons, which means that the manner ofelectron scattering changes depending on whether the spin directions areparallel or antiparallel in the two magnetic films of the spin-valvefilm included in the base. However, in the conventional spin-valvetransistor, diffusive scattering is mainly caused within the magneticlayer (F) or at the interface between the magnetic layer (F) and thenonmagnetic layer (N) as shown in FIG. 2A. In this case, since thescattered electrons are incapable of flowing into the collector due to astrong diffraction effect at the interface between the base and thecollector, the collector current is decreased. Therefore, in order toincrease the collector current, it is necessary to reduce the diffusivescattering. However, there arises a problem that the MR ratio is alsoreduced if the diffusive scattering is reduced.

BRIEF SUMMARY OF THE INVENTION

[0016] An object of the present invention is to provide a spin-valvetransistor capable of exhibiting a high MR ratio and a high ratio ofcollector current/emitter current.

[0017] According to an aspect of the present invention, there isprovided a spin-valve transistor comprising: an emitter, a basecomprising a spin-valve film in which two magnetic layers are stackedwith interposing a nonmagnetic layer between the two magnetic layers,and a collector, the spin-valve film having a stacked structure ofM/A/M′ or M/B/M′ and the spin-valve film being (100)-oriented, where Mand M′ may be the same or different and individually comprises at leastone element selected from the group consisting of Fe, Co, Ni and analloy including Fe, Co, Ni; A comprises at least one element selectedfrom the group consisting of Au, Ag, Pt, Cu and Al; and B comprises atleast one element selected from the group consisting of Cr and Mn.

[0018] According to another aspect of the present invention, there isprovided a spin-valve transistor, comprising: a spin-valve filmcomprising a first magnetic layer and a second magnetic layer stackedwith interposing a nonmagnetic layer between the first and the secondmagnetic layers, the spin-valve film being (100)-oriented; a firstelectrode electrically connected to the first magnetic layer; a secondelectrode electrically connected to the second magnetic layer; whereineach of the first and the second magnetic layers comprises at least oneelement selected from the group consisting of Fe, Co, Ni and an alloyincluding Fe, Co, Ni; the nonmagnetic layer comprises at least oneelement selected from the group consisting of Au, Ag, Pt, Cu, Al, Cr andMn.

[0019] According to still another aspect of the present invention, thereis provided a spin-valve transistor manufactured by a processcomprising: forming a first electrode on a substrate being(100)-oriented by epitaxial growth; forming a first magnetic layer onthe first electrode; forming a nonmagnetic layer on the first magneticlayer; forming a second magnetic layer on the nonmagnetic layer; forminga second electrode on the second magnetic layer, wherein the firstmagnetic layer, the nonmagnetic layer and the second magnetic layer areformed with a deposition rate within the range of 0.01 nanometers persecond to 0.1 nanometers per seconds.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0020]FIG. 1A is an energy band diagram of a conventional spin-valvetransistor;

[0021]FIG. 1B is an energy band diagram of another conventionalspin-valve transistor;

[0022]FIG. 2A is a diagram illustrating diffusive scattering ofelectrons at the interface between the magnetic and nonmagnetic layersof a conventional spin-valve transistor;

[0023]FIG. 2B is a diagram illustrating ballistic conduction andinterface reflection of electrons at the interface between the magneticand nonmagnetic layers of a spin-valve transistor according to anembodiment of the present invention;

[0024]FIG. 3 is a graph illustrating the energy band of Au in the[100]-direction;

[0025]FIG. 4 is a graph illustrating the energy band of Fe in the[100]-direction;

[0026]FIG. 5 is a graph illustrating the energy band of Cr in the[100]-direction;

[0027]FIG. 6A is an energy band diagram of a spin-valve transistoraccording to an embodiment of the present invention;

[0028]FIG. 6B is an energy band diagram of a spin-valve transistoraccording to another embodiment of the present invention; and

[0029]FIG. 7 is a cross-sectional view illustrating the spin-valvetransistor in Example 1 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The present inventors have found that, when a (100)-orientedspin-valve film having a stacked structure of a magnetic layer/anonmagnetic layer/a magnetic layer is employed as a base of thespin-valve transistor, it is possible to increase a ratio of collectorcurrent/emitter current (Ic/Ie) with retaining a high MR ratio. When thebase including the (100)-oriented spin-valve film is used, the diffusivescattering as shown in FIG. 2A can be suppressed, and instead, ballisticconduction or interface reflection of electrons is caused at theinterface of magnetic layer (F)/nonmagnetic layer (N), depending onwhether the spins of the two magnetic layers are parallel orantiparallel as shown in FIG. 2B. Namely, if a magnetic layersufficiently thin as compared with an electron mean free path in themagnetic layer is used and a flat interface between magnetic/nonmagneticlayers is formed so as to generate the ballistic conduction or interfacereflection of electrons, it becomes possible to provide a transistorthat exhibits a high ratio of Ic/Ie as well as a high MR ratio. Thereason why such effects can be obtained will be explained below.

[0031] Intensity of interface reflection of electrons at themagnetic/nonmagnetic interface varies depending on the band structuresin the magnetic and nonmagnetic layers. The band structures in variousmagnetic and nonmagnetic materials have ever been investigatedexperimentally and theoretically. The band structure is generallyrepresented in a wavenumber space, called the “Brillouin zone”. Forexample, the electrons travel in a crystal of Fe or Au in the[100]-direction can be represented by dots on the Δ line of theBrillouin zone. The states of electrons can be distinguished dependingon symmetric properties of wave functions, which are usually describedwith symbols such as Δ₁ and Δ₂ on the basis of irreduciblerepresentation of the group theory. The original point of the Brillouinzone is called a Γ point, and the states of electrons at this point canbe described with symbols such as Γ₁₂ and Γ₂₅ on the basis of the grouptheory.

[0032] Next, a specific example of combination of Fe(100)/Au(100) thatcan be epitaxially grown will be explained. The spin-valve film based onthis combination can be represented as M/A/M′. FIG. 3 shows the band ofAu in the [100]-direction. In FIG. 3, the ordinate represents energy ofelectrons, while the abscissa represents the wavenumber of electronsalong the Δ line of the Brillouin zone. As shown in FIG. 3, the band ofAu in the [100]-direction has Δ₁ symmetry in the vicinity of the Fermilevel. On the other hand, FIG. 4 shows the bands of Fe in the[100]-direction. As shown in FIG. 4, Fe has complicated bands, in whichthe up-spin bands have Δ₁ symmetry in a region over the Fermi level andthe down-spin bands have Δ₂, Δ_(2′) and Δ₅ symmetries.

[0033] Since electrons can travel between bands having the samesymmetrical property without being reflected, the up-spin electronshaving higher energy than the Fermi level and moving in the[100]-direction can pass through the Au/Fe interface. On the other hand,since electrons cannot travel between bands having a differentsymmetrical property, the down-spin electrons will be stronglyreflected. Namely, as shown in FIG. 2B, the ballistic conduction andinterface reflection of electrons with intense spin-dependency will begenerated. Therefore, it becomes possible to obtain an elementexhibiting a higher collector current as compared with the case wherethe diffusive scattering of electrons is generated with retaining a highMR ratio. Note that it is preferable to set the thickness of themagnetic layer to about 2 nm or less in order to suppress the diffusivescattering in the magnetic layer. The relationship between FIGS. 3 and 4can be obtained similarly even when Ag, Pt, Cu or Al is employed as anonmagnetic layer in place of Au.

[0034] Next, a combination of Fe(100)/Cr(100) that can be epitaxiallygrown will be explained. The spin-valve film based on this combinationcan be represented as M/B/M′. FIG. 5 shows the band of Cr in the[100]-direction. As shown in FIG. 5, the band structure of Cr has Δ₂,Δ_(2′) or Δ₅ symmetry in a region over the Fermi level, each of which issimilar to the down-spin band of Fe. Therefore, the down-spin electronscan pass through the Au/Fe interface, but the up-spin electrons will bereflected. Therefore, the ballistic conduction and interface reflectionof electrons with intense spin-dependency will also be generated in thiscase, although the relationship in transmissivity between the up-spinelectrons and the down-spin electrons becomes opposite to the case ofthe Au/Fe interface. The relationship between FIGS. 4 and 5 can beobtained similarly even when Mn, which has a similar band structure tothat of Cr, is employed as a nonmagnetic layer in place of Cr.

[0035] As explained above, it is important in the present invention thatthe magnetic layer and nonmagnetic layer forming the spin-valve filmincluded in the base are (100)-oriented. However, it is difficult togrow a (100)-oriented metal film on a IV-group semiconductor such as Siand Ge. On the other hand, it is known that a (100)-oriented metal filmcan be grown easily on a III-V compound semiconductor such as GaAs andInAs. Therefore, it is preferable in the spin-valve transistor accordingto the present invention that at least one of the emitter and collector,i.e., the underlayer of the base, comprises a III-V semiconductor.Specific examples of the III-V semiconductor include GaAs, GaN, GaP,InAs, InSb, and so on. In order to grow the (100)-oriented metal film onthe III-V semiconductor, it is preferable to perform surface treatmentof a substrate and to set appropriately a temperature of the substrateand a deposition rate of the metal film.

[0036] When a III-V semiconductor is used for the emitter in thespin-valve transistor according to the present invention, it ispreferable to form a collector made of a semiconductor thin film or astacked film comprising a semiconductor and a metal, the semiconductorof the collector having a smaller forbidden band width than thesemiconductor of the emitter, in order to obtain a further highercollector current.

[0037]FIGS. 6A and 6B show spin-valve transistors having a structure asdescribed above. The spin-valve transistor shown in FIG. 6A has astructure in which stacked are an emitter 31 formed of a III-Vsemiconductor thin film, a base 32 comprising an Fe/Au/Fe spin-valvefilm, and a collector 33 formed of a semiconductor film, which has asmaller forbidden band width than the semiconductor of the emitter. Onthe other hand, the spin-valve transistor shown in FIG. 6B has astructure in which stacked are an emitter 31 formed of a III-Vsemiconductor thin film, a base 32 comprising an Fe/Au/Fe spin-valvefilm, and a collector 33 formed of a metal thin film 331 and asemiconductor film 332, which has a smaller forbidden band width thanthe semiconductor of the emitter.

EXAMPLES Example 1

[0038] A spin-valve transistor comprising a (100) n-GaAs collector, a(100) Fe/Au/Fe/Al base, an Al₂O₃ tunnel barrier, and an Al emitter:

[0039] An example of fabricating process of the spin-valve transistorshown in FIG. 7 will be explained below. In order to grow a stacked filmof Fe/Au/Fe/Al epitaxially on a (100) GaAs substrate, it is required toremove an oxide film formed on the surface. First, the (100) n-GaAssubstrate 51 was placed in a multi-chamber MBE apparatus, followed byevacuating the chambers to about 2×10⁻¹⁰ torr, and then, in the firstchamber, the n⁺ GaAs layer 52 was homoepitaxially grown on the (100)n-GaAs substrate 51 to a thickness of about 1 μm to form a collector.The surface of the n⁺ GaAs layer 52 was observed with STM (scanningtunnel microscope) and RHEED (high-speed electron beam diffraction). Itwas confirmed that the surface of the GaAs layer was made into a 2×4structure terminated with As dimers. The width of a terrace of thesurface thereof was about 0.5 μm.

[0040] Incidentally, if the homo-epitaxial growth of the n⁺-GaAs layer52 is not performed, the GaAs substrate is subjected to etchingtreatment in a 10% ethanol solution of hydrochloric acid, and then thesubstrate is placed in a vacuum chamber, followed by heat-treating thesubstrate under a reduced pressure of not more than about 10⁻⁹ torr at atemperature ranging from 350 to 500° C. to remove an oxide film formedon the surface thereof.

[0041] Then, the substrate was transferred to the second chamber, andthen, by making use of Knudsen cells, an Fe film 531 having a thicknessof about 2 nm, an Au film 532 having a thickness of about 10 nm, an Fefilm 533 having a thickness of about 1 nm, and an Al film 534 having athickness of about 5 nm were successively deposited to form the base 53.In these processes, it was possible to obtain excellent (100)-orientedfilms when the deposition rate was set within the range of 0.01 to 0.1nm/sec. Thereafter, the substrate was transferred to the third chamberprovided with an Al source, and an Al₂O₃ layer having a thickness ofabout 1.5 nm was deposited on the base 53 under an atmosphere of about10⁻⁵ torr oxygen partial pressure to form a tunnel insulator 54. Theresultant substrate was transferred to the second chamber again, and anAl film 551 having a thickness of about 10 nm and an AU film 552 havinga thickness of about 100 nm were successively deposited as thin films ofthe emitter 55 on the tunnel insulator 54. Then, the junction area ofthe element was defined to about 50 μm×50 μm by means ofphotolithography and Ar-ion milling. Finally, CaF₂ was deposited to forman interlayer insulator 56.

[0042] An MR ratio of the transistor was measured while applying amagnetic field in the in-plane direction. As a result, when a voltage ofabout 1.3V was applied between the base and the emitter, the MR ratiowas found to be about 260%, and the ratio of Ic/Ie was found as high asabout 7×10⁻².

Comparative Example 1

[0043] A spin-valve transistor comprising a (100) n-Si collector, a(111) Au/Fe/Au/Fe/Al base, an Al₂O₃ tunnel barrier, and an Al emitter:

[0044] Fabricated was a transistor having a similar structure to that ofExample 1 except that a (100) Si substrate was used instead of the (100)GaAs substrate in Example 1. As a result, the base on the Si substratewas made into a (111)-oriented film, not a (100)-oriented film.

[0045] An MR ratio of the transistor was measured while applying amagnetic field in the in-plane direction. As a result, when a voltage ofabout 1.3V was applied between the base and the emitter, the MR ratiowas found to be about 230%, but the ratio of Ic/Ie was found as low asabout 4×10⁻⁴.

Example 2

[0046] Fabricated was a transistor having a similar structure to that ofExample 1 except that the junction area was set to about 1 μm×1 μm bymaking use of photolithography and Ar-ion milling.

[0047] An MR ratio of the transistor was measured while applying amagnetic field in the in-plane direction. As a result, when a voltage ofabout 1.3V was applied between the base and the emitter, the MR ratiowas found to be about 250%, and the ratio of Ic/Ie was found as high asabout 5×10⁻².

Example 3

[0048] Fabricated was a transistor having a similar structure to that ofExample 1 except that a stacked film of Fe/Cr/Fe/Al was employed as abase in place of the stacked film of Fe/Au/Fe/Al in Example 1.

[0049] An MR ratio of the transistor was measured while applying amagnetic field in the in-plane direction. As a result, when a voltage ofabout 1.3V was applied between the base and the emitter, the MR ratiowas found to be about 300%, and the ratio of Ic/Ie was found as high asabout 2×10⁻².

Example 4

[0050] Fabricated was a transistor having a similar structure to that ofExample 1 except that InAs was employed as a collector in place of GaAsin Example 1.

[0051] An MR ratio of the transistor was measured while applying amagnetic field in the in-plane direction. As a result, when a voltage ofabout 1.3V was applied between the base and the emitter, the MR ratiowas found to be about 260%, and the ratio of Ic/Ie was found as high asabout 2×10⁻¹.

Example 5

[0052] A spin-valve transistor comprising a (100) n-GaAs emitter, a(100) Fe/Au/Fe/Au base, and a Ge/Au collector:

[0053] A transistor having the titled structure was fabricated usingsimilar procedures to those in Example 1. In this transistor, theemitter was formed of the substrate and a Schottky junction was formedbetween the emitter and the base. The collector was formed of a stackedstructure of a Ge thin film having a thickness of about 10 nm and an Authin film having a thickness of about 100 nm. The Ge of the collectorhas a smaller forbidden band width than the GaAs of the emitter.

[0054] An MR ratio of the transistor was measured while applying amagnetic field in the in-plane direction. As a result, when a voltage ofabout 0.8V was applied between the base and the emitter, the MR ratiowas found to be about 260%, and the ratio of Ic/Ie was found as high asabout 3×10⁻¹.

Example 6

[0055] Fabricated was a transistor having a similar structure to that ofExample 5 except that a stacked film of (100) Co/Au/permalloy/Au wasemployed as a base in place of the stacked film of Fe/Au/Fe/Au in

Example 5

[0056] An MR ratio of the transistor was measured while applying amagnetic field in the in-plane direction. As a result, when a voltage ofabout 0.8V was applied between the base and the emitter, the MR ratiowas found to be about 300%, and the ratio of Ic/Ie was found as high asabout 1×10⁻¹.

[0057] As seen from the above explanation, the principle of the presentinvention can be applied to various materials, without being limited tothe combinations of materials set forth in the above examples. Namely,the principle of the present invention can be generally applied to anycombination of materials as long as the symmetry of the conduction bandin the nonmagnetic layer differs from the symmetry of the up-spin bandor of down-spin band in the magnetic layer at the interface of theoriented magnetic layer/nonmagnetic layer. The up-spin electrons aresubjected to intense interface reflection in the former combination ofmaterials, while the down-spin electrons are subjected to intenseinterface reflection in the latter combination of materials.Consequently, in any of these combinations of materials, it is possibleto provide a spin-valve transistor exhibiting not only a high MR ratiobut also a high ratio of Ic/Ie.

[0058] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A spin-valve transistor, comprising: an emitter;a base comprising a spin-valve film in which two magnetic layers arestacked with interposing a nonmagnetic layer between the two magneticlayers; and a collector; the spin-valve film having a stacked structureof M/A/M′ or M/B/M′ and the spin-valve film being (100)-oriented, whereeach of M and M′ comprises at least one element selected from the groupconsisting of Fe, Co, Ni and an alloy including Fe, Co, Ni; A comprisesat least one element selected from the group consisting of Au, Ag, Pt,Cu and Al; and B comprises at least one element selected from the groupconsisting of Cr and Mn.
 2. The spin-valve transistor according to claim1, wherein at least one of the emitter and the collector comprises aIII-V semiconductor.
 3. The spin-valve transistor according to claim 2,wherein the III-V semiconductor is selected from the group consisting ofGaAs, GaN, GaP, InAs and InSb.
 4. The spin-valve transistor according toclaim 1, wherein the emitter comprises a semiconductor thin film, thecollector comprises a semiconductor thin film or a stacked filmcomprising a semiconductor and a metal, the semiconductor in thecollector having smaller forbidden band width than the semiconductor inthe emitter.
 5. The spin-valve transistor according to claim 1, whereina thickness of the magnetic layer is sufficiently smaller as comparedwith an electron mean free path in the magnetic layer.
 6. The spin-valvetransistor according to claim 5, wherein a thickness of the magneticlayer is about 2 nm or less.
 7. The spin-valve transistor according toclaim 1, wherein a tunnel junction is formed between the emitter and thebase.
 8. The spin-valve transistor according to claim 1, wherein aSchottky junction is formed between the emitter and the base.
 9. Aspin-valve transistor, comprising: a spin-valve film comprising a firstmagnetic layer and a second magnetic layer stacked with interposing anonmagnetic layer between the first and the second magnetic layers, thespin-valve film being (100)-oriented; a first electrode electricallyconnected to the first magnetic layer; a second electrode electricallyconnected to the second magnetic layer; wherein each of the first andthe second magnetic layers comprises at least one element selected fromthe group consisting of Fe, Co, Ni and an alloy including Fe, Co, Ni;the nonmagnetic layer comprises at least one element selected from thegroup consisting of Au, Ag, Pt, Cu, Al, Cr and Mn.
 10. A spin-valvetransistor according to claim 9, wherein the first electrode is(100)-oriented.
 11. A spin-valve transistor according to claim 9,further comprising: a substrate formed on the first electrode, thesubstrate being (100)-oriented.
 12. A spin-valve transistor according toclaim 11, wherein the substrate comprises a III-V semiconductor.
 13. Aspin-valve transistor according to claim 9, further comprising: a secondnonmagnetic layer formed between the second magnetic layer and thesecond electrode.
 14. A spin-valve transistor according to claim 13,wherein the second magnetic layer comprises at least one elementselected from the group consisting of Au, Ag, Pt, Cu, Al, Cr and Mn. 15.A spin-valve transistor manufactured by a process comprising: forming afirst electrode on a substrate being (100)-oriented by epitaxial growth;forming a first magnetic layer on the first electrode; forming anonmagnetic layer on the first magnetic layer; forming a second magneticlayer on the nonmagnetic layer; forming a second electrode on the secondmagnetic layer, wherein the first magnetic layer, the nonmagnetic layerand the second magnetic layer are formed with a deposition rate withinthe range of 0.01 nanometers per second to 0.1 nanometers per seconds.